Heat exchanger having resiliently mounted tubular members

ABSTRACT

The invention relates to tubular heat exchange devices and in particular to improved arrangements of tube sheets for flexibly securing radiating tubes to the liquid containing chambers of the tube exchangers. Heat exchange devices commonly comprise a plurality of parallel tubes extending between input and output liquid containing chambers or liquid tanks. The temperature of liquid circulated by the tubes from the input to the output tank is modified by the region intermediate the tanks, commonly referred to as the cooling region. Each tank comprises a wall portion and a tube sheet or header. The tube sheet serves as a wall of the tank and secures the tubes thereto.

United States Paten m1 [111 3,739,840 Jones June 19, 1973 1 HEATEXCHANGER HAVING RESILIENTLY MOUNTED TUBULAR MEMBERS Inventor: SamuelPaul Jones, Erie, Pa.

General Electric Company, Erie, Pa.

Sept. 1, 1971 Assignee:

Filed:

Appl. No.:

US. Cl. 165/69, 165/175, 165/178,

29/l57.4, 425/110, 425/123 Int. Cl F28f 9/04 Field of Search 165/69, 79,173,

[56] References Cited UNITED STATES PATENTS l/1972 Young 165/79 X3,447,603 6/1969 Jones.... 165/178 2,225,856 12/1940 Buck.: 165/69 XFOREIGN PATENTS OR APPLICATIONS 158,778 9/1954 Australia 165/173 PrimaryExaminerAlbert W. Davis, Jr.

Attorney-Walter C. Bernkopf, Frank L. Neuhauser,

Oscar B. Waddell et al.

[57] ABSTRACT The invention relates to tubular heat exchange devices andin particular to improved arrangements of tube sheets for flexiblysecuring radiating tubes to the liquid containing chambers of the tubeexchangers.

3 Claims, 4 Drawing Figures PAIENIE JUN 1 9 ma 5 i a E/ HEAT EXCHANGERHAVING RESILIENTLY MOUNTED TUBULAR MEMBERS BACKGROUND OF THE INVENTIONSome cooling systems subject the tubes of the radiator to extremelylarge variations in temperature. For example, in the system described inU.S. Pat. No. 3,067,817 hereinafter referred to as dry type of heatexchanger," the tubes may pass liquids having a temperature in excess of-2009 F. or alternatively may be devoid of liquid and exposed to ambienttemperatures as low as 60F. Moreover, the hot coolant does notsimultaneously reach all radiating tubes or all portions thereof at thesame time so that individual radiating tubes are subjected to widelyvarying temperatures and temperature gradients. Thus some of theradiating tubes may be rapidly increasing in length due to the presenceof a hot liquid while adjacent tubes, having no coolant therein, mayremain contracted.

In arrangements of this type, it is essential to provide for a resilientconnection between the radiating tubes and the tube sheets. As disclosedin Applicants U.S. Pat. No. 3,447,603, it is desirable to utilize arigid tube sheet containing apertures into which tubes can be flexiblysecured so as to absorb thedifferential thermal expansions.Specifically, sleeves are resiliently secured thereto by an elastomericmaterial which is suitably bonded to the tube sheet and the sleeve. Thispermits the pattern to be maintained during curing so that the heatexchanger tubes can be readily installed in the sleeves, such as bysoldering, and also allows for individual movement of the tubes securedthereto.

Initially, it was attempted to mount the sleeves flush to the tube sheetso as to provide a flat plane on that surface of the tube sheet whichconstitutes the interior wall of the tank, i.e. the surface exposed tothe liquid in the tank. The bond between the sleeve and the tube sheetfrequently failed because of the shrinkage of rubber during the curingcycle, and additionally because of the action of the flux duringsoldering of the bonded sleeves to the tubes. This problem wasalleviated by positioning the sleeves to project inwardly into the tankpast the surface of the tube sheet and by extending the elastomericmaterial over substantially the entire surface of the tube sheet on thetank side. This arrangement was intended toprotect the tube sheet, whichwas usually made of steel, from the corrosive action of the liquid inthe tank. A perforated tube sheet was used having a bonded elastomericmaterial on each side. The perforations in the tube sheet were requiredto minimize blistering of the elastomeric material which subsequentlycan result in water leakage and failure of the system. However, evenconstructions utilizing perforated tube sheets were still subject toblistering and ultimate failure. It is believed that this deficiencyresulted from residual liquid deposits in the undrained areas of thetank which would initiate blistering. Heat exchangers, particularlythose of the dry type, are frequently mounted so that the tubes extendsubstantially horizontally one above the other. in some applications,the

heat exchangerassemblies are canted so that the plane comprising theparallel tubes is inclined slightly in respect to a vertical plane. Forexample, such canted assemblies are utilized in diesel electriclocomotives, wherein the assemblies are flush mounted in inclined.se'ctions intermediate the vertical side wall and the horizontal roofsection offthe locomotive. The canted location of the heat exchangerincreases the lower surface area of the elastomeric material which issubjected to residual liquid contained in the tank. Additionally, thesleeve and tube portions extending from the tube sheet into the tankpreclude complete draining of the residual liquid in the tank. l

The referenced U.S. Pat. No. 3,447,603 discloses one solution forfurther minimizing blistering and tube sheet failure. Therein theelastomeric material continues to be bonded to substantially the entiresurface of the perforated tube sheet which is exposed to the heatedfluidin the tank. However, the major portion of the surface area of theelastomeric material, which directly exposed to the heated fluid of theheat exchange system, is rendered vapor impervious, by a layer ofsuitable material, such as a metal or fluorocarbon polymer. Such anarrangement appears to further reduce blistering and rupture. However,the application of a vapor impervious material entails additonalmanufacturing steps and is very costly and time consuming. Additionally,the sandwich structure of this arrangement, wherein the layer ofelastomeric material is interposed between two water impervioussurfaces, may still be susceptible to blistering.

It is an object of this invention to provide a new and improved tubesheet arrangement for heat exchange devices which substantiallyovercomes one or more of the prior art difficulties and exhibitsincreasedoperating lifetime.

It is another object of this invention to provide such an improvedarrangement for heat'exchange devices which exhibits improved operatinglifetime while providing for less complex and expensive manufacturingprocedures.

SUMMARY Briefly stated in accordance with one aspect of the invention aplurality of radiating tubes are flexibly connected to tube sheets onfirst and second liquid containing chambers. Each tube sheet comprises areinforcing plate having a first surface constituting an interior wallportion of the chamber which is impervious to water vapor and isdirectly exposed to the liquid in the chamber. The plate is providedwith a plurality of apertures, displaced in a discrete pattern, but hasno other openings in the region which defines the interior wall portion.A plurality of sleeves adapted to be secured to the periphery of theradiating tubes, are provided with one sleeve being positioned withineach aperture. An elastomeric material is intimately and irreversiblybonded to substantially the entire area of the second surface of theplate to provide an elastomeric sur.ace on the side of the tube sheetdefining the cooling region of said heat exchanger. The elastomericmaterial is applied so as to further extend over substantially theentire external circumference of each of said sleeves whereby the onlyelastomeric material on the first surface of said plate within the areadefining theinterior wall portion of the chamber comprises discretecollars extending about each sleeve member. In this arrange- .ment, theelastomeric material and plate are arranged so that moisture migratingthrough the elastomeric material is not condensed and blocked by theplate to cause blistering.

The novel features believed characteristic of this invention are setforth with particularity in the appended claims. The invention itself,however, together with its organization and method of operation willbest be understood by reference to the following description taken inconjunction with the accompanying drawing in which:

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a perspective view of the heatexchange device incorporating this invention with the structural membersutilized in applying the elastomeric material.

DESCRIPTION OF PREFERRED EMBODIMENT FIG. 1 illustrates a heat exchangedevice comprising a plurality of heat exchange, or radiating, tubes 11extending between an input tank 2 and an output tank 4. The input tank 2has an outer wall portion 6 and an input liquid coupling 8. A first tubesheet 12 is connected to wallportion 6, by fastening means 17. Theoutput tank 4 has an outer wall portion 7 and an output liquid coupling9. A second tube sheet 13 is connected .to wall portion 7 by fasteningmeans 17. The tubes 11 extend between tube sheets 12 and 13 so that onefluid, such as water, may, for example be circulated through the tubesand a second fluid, such as air, may be circulated externally of thetubes. In order to increase the heat exchange between the fluids, theradiating tubes are generally provided with external fins 14.

Means are provided for resiliently mounting the radiating tubes betweenthe input and output tanks to accommodate individual changes in theirlengths under varying temperature conditions while maintaining a 3perfect liquid seal at all times. For this purpose the ends 'of theradiating tubes are each secured to a metal sleeve, or ferrule which hasbeen resiliently mounted to the tube sheet.

The arrangement for resiliently securing the radiating tubes to the tubesheets in accordance to the invention is illustrated in FIG. 2. The tubesheet comprises a reinforcing plate 18 constructed out of a suitablyrigid material. Steel plates have commonly been utilized for thispurpose. Although the liquid normally contains a rust inhibitingsubstance, it is desirable to utilize therefore a rust proof material,such as brass clad or coated steel, or a suitable plastic composition.The plate has a first Surface l9 which constitutes an interior wallportion of the tank chamber. As illustrated in FIG. 3, a peripheralregion 22 of said first surface is provided to contact an extendingportion of the outer wall portion 6 of the tank chamber and is fastenedthereto in a leak proof manner. A series of holes 26 may be provided inthe peripheral region to permit the plate to be screwed to thewallportion. Suitable gaskets of elastomeric material may be bondedabout these holes. These may be applied during the molding processdescribed subsequently.

The plate member comprises a plurality of apertures 16 punched, orotherwise suitably provided, in a preselected pattern. A sleeve, orferrule, is resiliently secured within each aperture as subsequentlydescried. Prior arrangements required a plate member containing pluralperforations intermediate the apertures. These were required in order toassist water migration and to minimize blistering. In such arrangementswater vapor penetrated the elastomeric material on the tank side andcondensed as it approached the cooled plate member. In accordance to theinvention, however, this problem is avoided and accordingly, the platemeinber has no openings interior of said peripheral fastening region,except for the aforesaid apertures 16.

The ends of the radiating tubes extend through the sleeves l5 and arerigidly secured thereto in a known manner, such as by soldering,brazing, welding, expanding or any other suitable means of providing arigid leak proof connection. One preferred method is to dip solder thetubes and sleeves subsequent to the sleeves having been resilientlysecured to the plate member.

The sleeves have an interior circumference adapted for rigid connectionto the radiating tubes and an and intimate length substantially greaterthan the thickness of the plate. As illustrated in FIG. 2, the sleeves15 are positioned within the apertures of the plate member so thelocomotive to extend substantially on each side thereof. The sleeves areintimately and irreversibly bonded within the apertures whose interiorcircumference is greater than the outer circumference of the sleeves.For this purpose a suitable elastomeric material of the type disclosedin US. Pat. No. 3,067,817 is utilized which effects an intimate bond tometal and which is capable of resisting the fluid employed in the heatexchange system. As described subsequently, it is particularly desirableto utilize an elastomeric material which may be applied by transfermolding techniques. One elastomeric material which is particularlysatisfactory is compounded from a silicon rubber gum sold by the GeneralElectric Company, Silicon Products Department under the designation No.CE-407. Such material is self-bonding and provides a very strong andintimate bond to the metal sleeves and the material of the member 18,which bond is not affected by the coolant at the temperaturesencountered, for example, in the locomotive engine cooling system shownand described in US. Pat. No. 3,067,817.

In accordance to the invention a layer 20 of the elastomeric material isbonded to substantially the entire area of the second surface 21 of theplate member, i.e. the surface exposed to the cooling region of the heatexchanger. Additionally, the elastomeric material is bonded tosubstantially the entire external circumference of the ferrules. Asillustrated in FIGS. 2 and 3, a surrounding collar of elastomericmaterial extends about the ferrule portions projecting on each side ofthe plate member. Thus a collar portion 25 extends outwardly into thecooling region from the second surface 21 of the plate and a collarportion 24 extends outwardly into the liquid chamber from the firstsurface 19 of the plate. This arrangement precludes bond failuresbetween the collar 24 and sleeve 25 due to flexures, curing shrinkageand actions incident to joining the tubes to the sleeves, such as theeffects of flux used in connection with the soldering operation. In thepreferred embodiment illustrated in FIG. 2, the opposing end portions ofthe sleeve 15 are flared outwardly. This flaring, in addition toassisting the insertion of the radiating tubes into the sleeves, isbelieved to contribute to the formation of an effective bond between theends of the sleeves and the elastomeric material. The curing shrinkageof the elastomeric material is believed to place the bond between theferrules and the elastomeric material under compression and thus improvethe elastomeric seal on the ends of the ferrules. Similarly, the abovedescribed arrangement is not subject to the blistering problemsencountered in described prior art arrangements, while obviating therequirement of costly perforated plates and the applications ofadditional leakage proof laminations on the surface of the elastomericmaterial. It is believed that the blister phenomena occurred in priorarrangements because heated fluid migrated through the elastomericmaterial, condensed upon contacting the plate member and was blockedfrom further migration by the plate member. In the present arrangementthe plate does not constitute a barrier to fluid which permeates throughthe elastomeric material. This permits retention of a layer ofelastomeric material on the plate which in addition to providingstructural support to the elastomeric seal between the plate and theferrules provides the manufacturing advantages described subsequently.The extending collars 24 and 25 about the sleeve while providing furtherstructural support to the seal between the plate and seal do not promoteblistering despite the absence of a vapor impervious coating about thesurface of collar 24, i.e. the elastomeric surface which is exposed tothe heated fluid in the liquid tank. Whereas the fluid vapors penetratethe elastomeric material of collar 24, the vapors freely migrate to theair cooled region of the heat exchanger without encountering a metalbarrier. Additionally, it is believed that the intermittent passage ofheated fluid through the radiating tubes minimizes the condensation ofvapors contained in the elastomeric regions surrounding the sleeves andtubes.

FIG. 4 illustrates a transfer mold arrangement for applying theelastomeric material. The mold arrangement, while not a part of thisinvention, is described to further explain the tube sheet arrangement. Afirst mold comprises a plurality of mold sections 32 which are secured,by screws 34 to a mold backing or support, plate 36. The mold sections,which are illustrated in cross-section, incorporate an extending annularmember 33 and an inner projecting member 38 so as to form therebetween atoroidal cavity. The projecting member preferably flares outwardly atits base. When the mold is positioned onto the sleeves 15, asillustrated in FIG. 4, the flared configuration of the projecting member38 flares the ends of the ferrules. The first mold is positioned so thatthe lower surface of the mold is displaced from the second surface 21 ofplate 18 by a distance corresponding to the desired thickness ofelastomeric layer 20. This can be accomplished by appropriate setting ofthe mold apparatus or alternatively by extension of screws 34, so that aportion of the screws extending outwardly of the mold sections providesfor appropriate displacement.

The wall of the projecting member abuts against the inner surface of thesleeve so as to prevent the application of elastomeric material to theinner walls of the sleeve. The inner wall of the annular member 33extends about the ferrule with a clearance equivalent to the thicknessof the elastomeric collar 25.

A second mold member abuts against the first surface of plate member 18.The second member is similar to the first comprising mold sections 42secured by screws 44 to a mold support plate46.

During the transfer molding operation, the elastomeric material isintroduced through one or more sprues 37 of the first. mold against thesecond surface of plate 18. The elastomeric material thus forms layer 20and by entering the cavities of the mold sections 32 forms collars 25.Additionally, the elastomeric material flows through the annular spacesformed by apertures 16 and sleeves 15 into the cavities of the moldsections 42 to form collars 24. Accordingly, the application of theelastomeric material can be performed in a single transfer moldingoperation. The application of layer 20 not only provides structuralsupport, but additionally obviates the requirement to include spruesinto each individual mold section. Various modifications may be made inthe molding operation and the structural parts used therefor.

The above described arrangement provides a reliable arrangement forresiliently securing radiating tubes to the liquid containing tanks ofthe heat exchanger. It minimizes bonding failures, and provides foreconomies of manufacture and parts. While only a preferred embodimenthas been described in detail herein, it will be apparent to thoseskilled in the art that many changes and modifications may be madewithout departing from the invention in its broader aspects. It isintended therefore, in the appended claims to cover all such changes andmodifications as fall within the true spirit and scope of the invention:

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. In a tubular heat exchange device wherein a plurality of radiatingtubes are flexibly connected between first and second liquid containingchambers, each chamber comprising:

a. an outer wall portion;

b. a reinforcing plate having a first and a second planar surface;

0. means for fastening a peripheral fastening region of said firstsurface in a leak proof manner to said outer wall portion, said firstsurface of said plate constituting an interior wall portion of saidchamber directly exposed to any liquid contained therein;

(1. a plurality of sleeve members having a longitudinal lengthsubstantially greater than the thickness of said plate, an interiorcircumference adapted for rigid connection about one of said radiatingtubes, and a predetermined exterior circumference;

e. said plate comprising a plurality of displaced apertures having aninterior circumference greater than the external circumference of saidsleeve members; said plate having no openings interior of saidperipheral fastening region, excepting for said apertures; one of saidsleeve members being disposed within each of said apertures;

g. an elastomeric material intimately and irreversibly bonded tosubstantially the entire area of said second planar surface to providean elastomeric surface on the side of said tube sheet defining thecooling region of said heat exchanger;

h. said elastomeric material further being intimately and irreversiblybonded to substantially the entire external circumference of each ofsaid sleeve members, whereby the only elastomeric material on the wardlyand the elastomeric material extends about the external circumference ofsaid sleeve members to form collars extending from each end portion tosaid plate member.

3. The arrangement of claim 2 wherein the elastomeric material comprisesa self-bonding silicon rubber material.

1. In a tubular heat exchange device wherein a plurality of radiatingtubes are flexibly connected between first and second liquid containingchambers, each chamber comprising: a. an outer wall portion; b. areinforcing plate having a first and a second planar surface; c. meansfor fastening a peripheral fastening region of said first surface in aleak proof manner to said outer wall portion, said first surface of saidplate constituting an interior wall portion of said chamber directlyexposed to any liquid contained therein; d. a plurality of sleevemembers having a longitudinal length substantially greater than thethickness of said plate, an interior circumference adapted for rigidconnection about one of said radiating tubes, and a predeterminedexterior circumference; e. said plate comprising a plurality ofdisplaced apertures having an interior circumference greater than theexternal circumference of said sleeve members; said plate having noopenings interior of said peripheral fastening region, excepting forsaid apertures; f. one of said sleeve members being disposed within eachof said apertures; g. an elastomeric material intimately andirreversibly bonded to substantially the entire area of said secondplanar surface to provide an elastomeric surface on the side of saidtube sheet defining the cooling region of said heat exchanger; h. saidelastomeric material further being intimately and irreversibly bonded tosubstantially the entire external circumference of each of said sleevemembers, whereby the only elastomeric material on the first surface ofsaid plate and within said peripheral fastening region comprisesdiscrete collars extending about each sleeve member and fluid vaporspermeating said elastomeric material from said liquid containing chamberare not blocked by said reinforcing plate so as to avoid formation ofblisters within said elastomeric material.
 2. The arrangement of claim 1wherein each of said sleeve members has opposing end portions flaredoutwardly and the elastomeric material extends about the externalcircumference of said sleeve members to form collars extending from eachend portion to said plate member.
 3. The arrangement of claim 2 whereinthe elastomeric material comprises a self-bonding silicon rubbermaterial.